Date Modified & Time modified + Date entered & Time entered

I can’t read code and previously found this really easy to read article to enter in my date modified timestamp and I messed it up when I was trying to edit it for a second column for date and time entered. I need a code for dummies column M starting at row 2+ I need a code for date and time modified. Column N is for date entered and time entered. My second sheet my date modified is one column in (it’s one column shorter than the first sheet). I would have asked this on an existing page but this website wouldn’t let me comment. Please help.
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